Any insight into this phrase? They have been talking about it on the Facebook New Testament Greek Club. The conventional wisdom is that there is some sort of ellipsis to make sense out of what looks like an accusative feminine plural, but I'm wondering if it isn't something else, a frozen form either adverbial or neuter singular that survives only in this phrase (it is attested in Classical literature and the papyri, and is sometimes written as one word). Does Horrocks mention it in his History of the Greek Language?

I have looked at this before, wondering about it. I probably won't be much help here but I believe Blass and Robertson take this as an ellipsis of "odos" or "way." (I am doing it both ways to eliminate confusion.) I also believe a ounce treats this as one word in his lexicon and morphology. When I first encountered it, I just assumed it to be an idiom. I don't know if this helps at all.

"We cannot teach people anything; we can only help them discover it within themselves."-Galileo Galilei

Since we're speculating, I suggest it has something to do with "selfies" originally. Or maybe it started with the sense "just among us ladies" and then got generalized to mean "far from the madding crowd. BDAG lists it, as does BDF, as idiomatic, even written as one word καταμόνας, like καθόλου.